Apparatus for making magnetic recordings



July 5, 1960 A. H. DICKINSON APPARATUS FOR MAKING MAGNETIC RECORDINGS Filed April 16. 1954 '7 Sheets-Sheet l hhhhhhhhhll- LMLA Z I )8 INVE NTOR BY TTORNEY 1960 A. H. DICKINSON 2,943,907

APPARATUS FOR MAKING MAGNETIC RECORDINGS Filed April 16, 1954 7 Sheets-Sheet 2 uymvrox July 5, 1960 A. H. DICKINSON 2,943,907

APPARATUS FOR MAKING MAGNETIC RECORDINGS 7 Sheets-Sheet 3 Filed April 16, 1954 Fig July 5, 1960 A. H. DICKINSON APPARATUS FOR MAKING MAGNETIC RECORDINGS Filed April 16. 1954 '7 Sheets-Sheet 4 w w 51 R 1N VIFN TOR.

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APPARATUS FOR MAKING MAGNETIC RECORDINGS '7 Sheets-Sheet 5 INYENTOR.

July 5, 1960 A. H. DICKINSON 2,943,907

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APPARATUS FOR MAKING MAGNETIC RECORDINGS Filed. April 16. 1954 7 Sheets-Sheet 7 VOLTAGE 5K6 Voltage across Res/sr0r7/4 Vo/gage of D/schargmg Keyboard Condenser Card Feed 1N VENTOR F/GI 4 4x74 fiw United States Patent APPARATUS FOR NLAKDIG MAGNETIC RECORDINGS Arthur H. Dickinson, Greenwich, Conn, assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Apr. 16, 1954, Ser. No. 423,816

' 14 Claims. (Cl. 346-74) This invention relates to a method of representing numerical data and to apparatus for producing such representations.

More specifically, this invention relates to a method and apparatus wherein magnetic recordings of numerical significance are made on a magnetizable medium such as a magnetizable IBM card wherein each digit is represented by a different discrete magnetic condition resulting from a distinct rate of change in the voltage applied to the recording head of a magnetic recording instrument during the recording of the digit whereby different electronic responses are obtained in an electronic computing machine from each different magnetic recording.

In the application Serial No. 423,774 to Arthur H. Dickinson, filed April 16, 1954, concurrently herewith, there is described a method for utilizing such cards in an IBM electronic computing machine in lieu of the cards wherein each digit is represented by the position of one recording in each column of the card. By this invention the number of digits that may be recorded on a single card is not limited to the separate columns permitted by the width of the card but is multiplied by the number of separate rows of magnetic recordings that may be impressed on the card without overlapping, and the capacity of the computing machine for the same rate of the cards therethrough is correspondingly multiplied.

It is well known that the density of the remanent flux in the magnetized areas of a card or other recording media are proportional to the magnetomotive force applied in the making of the record and that the electric currents initiated by the passage of such magnetized areas in operative relation with a responsive pick-up coil will vary in accord with the remanent flux density. Hence, if the rate of change of the voltage applied to the magnetic recording head from zero to a desired maximum is different for each digit during its passage past the recording head, the nature of the electrical response during the passage of each recording past the pick-up head in the computing machine will be different for each digit. In the method of recording herein described, the time interval of recording each digit is the same during a portion of which time interval the flux density in the magnetized portion ofthe passing card is built up from zero to a maximum and is continued at this maximum for the balance of the time interval, the portions of the interval duringwhich the magnetic flux is built up and, inversely, the portions of the interval during which the maximum magnetic flux is impressed being different for each digit.

For carrying out my invention I have provided a machine for producing in magnetizable IBM cards successive rows of recordings by means of a series of recording heads, one for each column of the card, all the recordings in each row being simultaneously made during the successive movements of the card and in such machine I have utilized various structural features of the standard IBM card punching machine such as the keyboard, card magazine, etc. modified as required. In the accompanying drawings I have illustrated a machine having thirty ice recording heads for cards having thirty columns but any number more or less may be employed.

In the said drawings:

Fig. l is a front elevation of the machine;

Fig. 2 is a vertical sectional view on line 2--2 of Fig. 3 showing a portion of the driving mechanism for the card feed; a

Fig. 3 is a plan view of the card feeding mechanism as it appears with the top wall of the casing removed;

Fig. 4 is a side view of the machine with the upper portion of the machine in section on line 4-4 of Fig. 3;

Fig. 5 is a side view, partly in section, of the keyboard;

Fig. 5a is a sectional view on line 5a5a of Fig. 1;

Figs. 6, 7 and 8 are detail views of three cam operated switches which control certain steps in the sequence of operation;

Fig. 9 is a diagram showing the magnetic recording instrumentalities and the control circuits;

Fig. 10 shows the wave pattern of the oscillating current in recording the digit 7, and illustrates graphically the impressed voltage during the recording of the digit;

Fig. 11 similarly illustrates the impressed voltage in recording all the digits; and

Fig. 12 shows a card with the recordings indicated as in Fig. 11.

For each column of card capacity there is provided a separate keyboard section, and separate erasing heads and recording heads. For each key there is provided a separate condenser, the capacity of the condensers being different for the different digitsrepresented by the difierent keys and the difierent discharges from these condensers of difierent capacity are utilized to difierently modify the operation of the recording head to produce in the card a different recording for each digit of the character above described.

The machine is equipped with the usual reciprocating picker mechanism for advancing the individual record cards from the card magazine to a pair of feed rolls which serve to advance the cards at each operation past the erase and record heads the distance required for making one row of recordings across the card. The initial feed movement of the card from the magazine brings it to rest in position to receive the first row of magnetic recordings. The keys representing the digits to be recorded in the several columns are then punched, the keys being held down by a suitable latch mechanism. As each key is depressed the condenser associated with it is operatively connected to the magnetizing circuit of the recording head for that column so that the recording in that column will represent the digit indicated by the depressed key. After the proper keys in all the columns where recordings are to be made are depressed, a switch is closed by the operator, whereupon the feed rolls are operated to advance the card with respect to the recording heads, the recording head circuits are energized, the proper recordings are made in each column where a key was depressed, the depressed keys are released, the ,re-

cording head circuits are opened and the feed rolls are stopped with the card in position to receive a second row of recordings. When thedesired recordings have been made in all the rows, a second pair of feed rolls carries the card to the stacker. When this second pair of feed rolls is set in motion at the completion of the final row on the card, the card feed picker is actuated to feed a second card from the magazine and the first pair of feed rolls are operated for a prolonged period sufiicient to bring the second card into position to receive row of recordings.

For each record cycle the card is advanced.one quarter inch whereas the feed movement required. to bring the card into position for the first record cycle the first requires a movement of three and a half inches. This dual operation of the feed rollers is accomplished by a differential gear mechanism which will now be described along with the other mechanical features of the machine. These distances are optional and are Ithose'requifed to .make twelve rows of'r'ecofdings on an'IBM card of usual dimensions. 7

Referring particularly to Fi'gs. '1, 2 and 3 thema'chine comprises-two sections, the keybeard section and a card feeding' an'd recording section. -"As thebotiifiefhtidh'fbetween the two sections is entirely electrical, the two sections :may be :physically separate but 'ordinar ily the two.5sections willfzbe embodied in'a' single machine-as shownfl i 'I he'machine comprisesa base 1 on the rearwardpart 7 of which the card feeding mechanisms -are mounted.

This portion of the machine has three vertical frames or 'walls "'2, 341116 4 .(see Fig.3). "lournalled in walls 2 and '4 is a sha'ft'5 which operates the picker knives of the card 'magazine in the usual manner.

lo'urnalled in frames 3 and 4 is a shaft 6. Shaft 6 carries the usual cam Sm-which oscillates shaft'5 of'the picker knives in order to feed the bottom card from the hopper into the V 'first pair of feed rolls.

The picker mechanism is of usual construction and willnot the further described.

.Rotatably rno'unted'on shaft 6 is asingle toothed .dr-ivin'g 'e'lement'7 which is integral with a gear8. Gear 8v meshes with a gear 9 which is .rotatably mountedon a cause rotation of gear 25 in a counterclockwise direction shaft 10 jour'nalled in the frames '3 and '4. Gear- 9 is integral with a similar single notch driving elementfll. Meshing with gear 9 is a gear 12 which inturnmeshes with 'a gea'r'1'3 mounted on the motor shaft 14. It will In the same way, shaft 10 is normally held against rotation by. clutch arm 19 which is engaged by. armature latcharrn '25 'andfkeeper 21. By. this arrangementshaft 6 will be given. one complete revolution from the motor shaft whenever the circuit through the magnet 34 which controls the armature 17' is closed 'and shaft It) will be given one complete revolution when .the circuit through magnet '36'of the armature 20 is closed. a

v Referring to Fig. 3, shaft 6 has .jpinnedito it theicr'oss shat-T 22 on which are rotatably :mounted two .Zbev'el pinions23 and 24"forn'1ing part of the above-mentioned differential gear. These pinions '23 and 24 mesh with .a bevel gear '25 which is integral with a'spur gear -26 and is rotatable on shaft 6. Pinions'23 and 24..also mesh with a bevel ge'ar 27 which is integral witha'spur gear 328 and jis alsor'ota'table on shaft 6. Theupp'er shaft29 0f the'first' pairfoffeedrollsis driven through'fhisidifierential and when'fsh'aft 10 is the member fdf the differential the feed rolls will feed the. .car'da distance of one-quarterQinch asreqnir'ed -for each-record cyele and when shaft fi-is' ithe'driving member of theairrerental as indicated by the arrow. As gear is integral with gear 26 which meshes with gear 35, fastened to the feed roll shaft 29, the feed rolls will be rotated a sufficient amount to feed a card the three and one half inches required to bring the card to the required initial position.

As previously explained, shaft 6 carries the usual cam which oscillates the picker knives and the dimensions of parts is such that one revolution of shaft 6 is suflicient to feed 'a card fromthe magazine into the first'pair of feed rolls and cause it ing position. r p

The cards are of a size topre'ceive twelve separate rows of recorded digits and after the card is fed to the first recording position it :is advanced in increments of onequarter inch at a time, during which movement the successive magnetic recordings are made in separaterows across the card. These successivemovements for each record cycle are accomplished byenergization of magnet 36 to impart a single revolution to shaft 10 and to gear fastened thereto. Gear 30 drives gears 31 and .32

and gear .32 in turn drivestheige'ar 28 rotatably mounted on shaft .6. Gear 28 thus serves as they driving gear'o'f the differential and through thepinions Band 124. .As the cross shaft 22 is held stationary byshaft "6.:pi i6ns '23- and 24 rotate on their'own axes and drive gear '25.

Due'to the gear reduction between shaft 'l0 andIge ari-2 s 7 one revolutionof shaft 10 rotates feedroll shaft. 29 a correct .amount to feed the card the linear distance re- 7 qiiire'd'for one record cycle, that -is, one-'quarter;inch.

During this recording cycle the circuit of magnet36'is opened so that the card comes to rest and remains so until-the keys 'are punchedto select another row of digits to be recorded during the succeeding cycle. The recording heads 656 are positioned as shown in advance of the first pair of feed rolls and the erasing heads 654 positioned between the feed rolls and the recording heads to'insure a complete demagnetization of the-card'be'fore it reaches the recording heads.

The cards are supported in theirpassage beneath the These rolls are driven in unison with the first pair ,-of

thelfeedrolls will advance the card the. three fando'ne half inches required tofeed "the card delivered-from the 'magazine -to a position to receive the first recording.

A gear -30 'is fastened "to shaft 10 and meshes a gear 31 which, with an integral gear 32,. are mounted on astud'33. Gear. 32 .-in turn meshes withithespur gearf28 whichl is integral with bevel gear 27 of the difier-l ential. Hence; when .shaft 10 is held against rotation by armature .l'atcli '20,"b'evel gear 27 is alsoheld against rotatio'n.

7 If the magnet 34 energized, it willfa'ttract the'armw ture latch '17 and release the dog"16'ther'.eby"imparti r 1ga 6 .'a'. rotation. Shaft 6, in rotating, W111 rolls by a gear 41 on the shaft 29 of the first.pairfof rolls, an intermediategear 42 and a gear 43 on theshaft of the upper roll ofthe second pair. Beneath the cards is a switch ,63 whose upstanding .arm is in the path of the card so that the switch is closed, wheneverialcard is present (see Fig. 4);

At "the conclusion of the predetermined number .of recording cycles the magnet 34 is again energized to drive the feed rolls from the shaft 6 and thereby advance the finished card into the receiving hopper and bring another card into position for the first recording.

The keyboard comprises thirty columns of individual keys. There are ten keys ineach columnbeing numbered O'throngh 9 .(see Fig. 5.) Each key 44 is no rrnallyrheld in elevated position by an associated spring45 and islatched in the depressed position by a latch bar 46 (of which.

one is provided for each .column of keys) Each -key bar 47 is provided with a v shaped conducting portiq zts adaptedto engage, u'po'n depressionof the associatedkey,

the related contact 49. Thesenner'nbers 48 and 493011- stitute the switch whereby the condenser 'ofi thelpro'per capacity for the particular-digit represented by theykiey is 'conn'ected to the magnetizing circuit. a 7

7 n addition to the latch -bars-46, supplemental controlor no entry bars 50 are also provided one for each column of keys. Upon the depression of any key in 'awcolumn the corresponding bar 50 is -cammed outwardly (-to th'ej right as viewed in Fig. against the actir'rn 'of"spring by thecamming edge 52 on-key-bar-47 in" cooperation with the stud '53 fastened to no entrybar 5t). 'The 'oiltto be advanced to the first re'cor'd asaaoor ward movement of such bar is adapted to open contacts 686, the effect of which will be later described.

Also mounted on the keyboard is a motor bar 54 which is depressed to initiate the recording cycle after the selected keys are depressed (Fig. 5a) By means of a latch lever 55, the depressed bar is maintained so, due to the engagement of the bar with the latch lever. The motor bar 54 is released near the end of a recording cycle by means of a solenoid 56 which is energized to restore the motor bar to its normal position. The energization of the solenoid 56 causes the latch lever 55 to be partially rotated in a clockwise direction, thereby releasing the latched stem of the motor bar. During the said rotation of the latch lever 55 and after the release of the motor bar, the link 57 causes lever 58 to be partially rotated and in turn to rotate the shaft 59 in a counterclockwise direction. Shaft 59 extends across the keyboard and at each end has an attached arm 60 whose outer ends are connected by a transverse bail 61 contacting the rear ends of the latch bars 46 and which, upon being rocked, thrusts the latch bars 46 forwardly releasing the depressed keys which have been latched down.

Also mounted on the keyboard is a card feed switch 62 which is closed to advance the first card from the magazme.

Fig. 9 shows the control circuits of the machine. It is placed in operation by closing SWL which supplies AC. power to the drive motor, filament transformer and the input to the DC. power supply. The filament wiring has been omitted and the DC. power supply shown in block form only for simplicity. After the vacuum tubes have reached their operating temperature and DC. potentials are supplied to wires 74, 76 and 78, the device may be operated. As indicated, 76 is the ground wire of the DC. circuit and 78 has a negative potential with respect to 76.

Having placed magnetizable cards in the hopper, it is now necessary to advance the first blank card up to the record position. The card feed switch 62 is closed and a normally discharged condenser 610 is charged through contacts 612 and through relay coil R3. R3 is thus momentarily picked up during the charging of condenser 610 and a circuit is completed from wire 74, wire 618, through points 614, via wire 620, through points 622 and clutch magnet coil 34 to wire 76. Shaft 6 is thus given one complete revolution and the first card is fed to position to receive the first row of recordings as previously described. Near the end of the card feed the leading edge .of the card engages the upstanding arm switch 63 and closes the switch, thereby energizing relay R1, current flowing from wire 74, through 618, 624, switch 63, relay coil R1 to wire 76. Relay R1 remains energized until switch 63 again opens. The proper keys for the first ena record cycle and feeds the card the required linear distance for one recording through a single revolution of shaft 10. Shaft has attached to it three cams which respectively open and close three switches C1, C2 and C3 through which the sequence of operations during the recording cycle is secured. When the shaft 10 has turned through approximately 36 switch C1 closes momentarily .thereby completing the circuit through the coil of relay R2 from wire 74 through wires 618, 624, through C1, now closed RIB contacts 630, through R2 coil to wire 76. When R2 picks up, it is held up through its hold points 652 (R2B) and normally closed C2 contacts 634.

At approximately 36 before the rotation of shaft 10 is completed, cam contact C2 momentarily opens breaking 6 the R2 holding circuit and R2 drops out. It is during this interval that the actual recording takes place.

The recording heads 656 and erase heads 654 are of conventional design and are similar in appearance. The recording heads are designed for use with a high frequency biasing voltage which enables virtually distortionless recording. Since this method of magnetic recording is well known in the magnetic recording art and is employed in many applications, further discussion of its operating characteristics will not be given here. The erase heads are constructed with larger, non-critical gaps and are located ahead of the recording heads as .the card passes through the machine. 3

Two sine wave oscillators (not shown) of the type commonly referred to as Series Fed Hartley Oscillators are employed. The output of one is approximately 5 kc. and the output of the other is approximately 50 kc.

The low frequency oscillator is the source of voltage ap-- plied at various rates of increasing amplitude to the recording head. The high frequency oscillator is the source voltage for the erasing head and also serves as the source voltage for the high frequency bias supplied to the recording head.

The erasing process is accomplished as follows. The output of the 50 kc. oscillator is fed via wire 668 to the grid of a cathode follower 670 (see Fig. 9). Since there are 30 erasing heads in the device, the cathode follower 670 functions as an impedance matching device to prevent overloading of the transformer of the oscillator. The resulting high frequency voltage appearing across resistor 672 is applied through condenser 674 to the erase head 654.

By feeding a relatively high voltage to the erase head sufiicient stray flux is produced near the lagging and leading edges of the gap to subject the magnetizable area on the card gradually to an increasing and then a constantly decreasing field. At conventional machine speeds, each magnetic particle in the card is subjected to well over gradually decreasing cyclic fields within .025" of card travel which is more than adequate number of reversals to completely erase any material on the card.

The voltage across the resistor 672 is also applied from the tapped point through resistor 676 and condenser 678 to the recording head 656 as a source of high frequency bias. Its level as it appears on the recording head may be adjusted by moving the tap on resistor 672. During a recording cycle, there is mixed with this bias voltage a modulated 5 kc. voltage having a waveform representative of the digit selected in the keyboard. The method of producing these modulated 5 kc. waveforms will now be described with reference to Fig. 10 wherein the recording for digit 7 is illustrated.

When the number 7 key is depressed in the number one column of the keyboard contacts 48-9 through the condenser 688 of the ,7 key are closed and contacts 686 opened. Contacts 686 open whenever a key is depressed in "a column and remain closed if no selection is made. One side of condenser 688 is connected via wire 690 to the ground line 76. The other side is connected via wire 692 through a low value current limiting resistance 7 10 to the cathode-anode junction 694 of triode 698 and pentode 706. The grid 6% of triode 698 is connected .to the positive line 74 of the DC. circuit through resistor 700 via wire 702, wire 628 through normally closed contacts 608. Thus, the grid potential of triode 698 is near that of line 74. The cathode of miode 698 is then also near line 74 and when the #7 key was depressed in the first column, condenser 688 was charged up to the potential difference existing between junction 694 and ground. Triode 698 is a charging means for any keyboard condenser selected by the depression of a keyboard key. Pentode 706 is a constant current discharge means for discharging the selected condenser during the recording cycle at a constant rate. The rate of discharge is directly proportional to the value were? Qje apa qitanceinvolved hec ause the discharge current is .533 charges th ough relay" coil R5; which closes con- 5 consta t; adiust ment in thegridiil bias by means tact 640T'So1enoid'jcoil' 56 is thus ener d v ota, potentiometer in the grid resistor circuit may be made ates to clear the keyboard and release th t9 a iustthepentode anode current. A voltage regulator s's tpevfe'dser'ibes. Should it assesse to clear tuhe is prhyided to maintain constant screen poten- 5 keyboard without maiking an entrygth ey ssrsisrma'y tial tqrnentqde'l-fl .fQr. inea it rb dep 1511s P i up ieIay 5 6 ms ..A In. a reeording cycle, when relay R2 picks up contoenergize the solenoid 5 6: l t fitm on relay open. when contacts Q38 open, Fig. ll shows the shapes of the magnetized areasprosue by de res i es s ek v ni 's 'as in! noint i718 assumes thepot nt al f i e .3, mor ne V tire. than ground. Since grid 696 of :trio'de 623 is con- 10 dicated by the numbers under each shapejland "Fig. l2 lo Tnected through resistor. 1531} Via wire 2' h 99 m lW$ an M a 511911 5 95 ailq P'iFli at; conduction through'thisitliode ceases and the constant machine with typical magnetized areas as prqdu d by current flow in pentode 70.6, begins to discharge oonthe rnaehine.-

denser 1588. As condenser 688 discharges, the potential As pointed out above, the capacities of the co densers sat-junction "694 begins to decrease at a constant rate dish vary in proportion'to the values of the lgliSYf/lll ll and' -cont'inuesto do'so. Junction v694 is connected to they represent; and as the cards are fed at a constant the gi idfof'tiiode 104Twhi6h gates the output of 'a cathrate, the resulting magnetized areas vary in shape :as

dde' fol-lower'llz int he following manner. The output shown. That is to'say; the recordings produced by a ofthe 5 kc. oscillator is fed via wire '716 to the gridof circuitincludiug a condenser hayingther greater capacity diode 712." "Since triod e"71 2 ,i'sconnecte'd as a cathode and consequently the greater rate of, discharge, eghthe {follower} were' it not for the action of triode 7tt4,wthe circuit for digit f9,, will have a shorter portion of d evoltage" ac'rossresistor 714" wouldreaeh' positive valu'e creasing Width than the recordings producedfby the cirapproximately equal to the positive excursion of the grid 'cuits of the smaller digits; e v of '7l2if'iAs was 'pf 1I2 decreases in potentialf'the .Cam switch C3 through contacts 646 is used to autovoltage acrossthefcathoderesistance 114" would" similarly mati cally advance a new card when 12 rows have been d 'se"tintilzerofdrop 'was reached. During the negarecorded on apreceding 'card. Asthe card advances tive avelf'o '7 l 2fgrid, the voltage'would remainat 'zero. through the 12th recording cycle; it passes beyond "the snsge a ra s Tres istof714 "therefore" would increase card contact switch .63 and drops out relay R1. Contact max; um and sms zero SL000 times 'p'er's'econ'dQ 1546 closes just before shaft 10 completes-its rotation and so eonne'cted'as' a cathode follower and'ith'e R6" relay coil is momentarily pickedup durin -the char potential on its gndnetirh nss voltage'drop ing' of condenser 648. The charging currentfor 'th'is agross resistor 11%. Normally with junction 694 at: its condenser 'flows from wire 74,th.rough wire 618; con point, the conduction of triode 704 is such denser 6&8 now closed RIC points 650 through cam can c 0 put voltage appears'across resi'stor gle creaslesfin potential, duninga regard 'los'es'RoA contacts :652 to energiz'e'the card feedclutch As t i cm" Q4 aven 'a r ess 114.. 1 5 like t ,It returned, however 'to its original peak 7 tacts652,fwire 621} and contacts dfid -The card feed :clutch is thus automatically tripped atithe en'd ofthe 12th recording cycle on each card and feeds the' 1 1ext card up'to the record position. In the foregoing specification I 'haye described my inrnetic records on IBM magnetizable cards but' it will be understood that other mediums, may be employed'f h as tape of magnetizable' material. I It will also be understood that means other than the V V described keyboard may be employed selecting "the across resistor .714lissuch'that on its negatiye'e iy'aluejs to be recorded and that the control circuits are *FilisiQgiljehitieW-Z? iilsifuti'qff, s vs s coi ithe features'of th pp r t s and m=1 1iQ i9 I -denser 8 ,-continuesto discharge beyond a certain point ftion may be variously modified in adapting'the'inyen no further increase in the .yoltage across potentiometer 10 d eren purposes. It is "therefore to d d QS Z'occurs. -ZFig. 10 shows the waveforms at the yarious tha h invention is qtli te l hsis ssifis 3 h points discussed. I t apparatus herein described but includesall SIl Clil' IlflQtllfi By'means just described, the digit representing wavel O t r as fa l Within theseope fthe amended forms consistingof a modulatedenvelope of 5 kcjvoltmsage-are caused to appear across potentiometer 682 during I'C a V v the recordingtpeniod. The level of the voltage maybe a PP U ma .Hlfigltsii rtjccqrdin 29. 1 adjusted for optimum by the potentiometerGSZ and is prising means for v n i fi gi t able'rnediu applied through condenser 680 to recording head 656. 7 recording headpositionddta i h pa hofm lefilelit r ghayinga glrey depressed does not receive any'recording.

' Gin the cqlumn to which it is related Jand asta result the -ping in potential rsincetitiisr directly connected through a applying :said redording head fd iil g $9 1 ilowilmpedail 71,0 and through icontactsofid to mam. V t rare xqd o -n' eg e m ned dur s nas l -Neai theiend of th e;r e cord cycle the holdupcircuit of ,c urrent of predetermined alid i q 'mr f.

tCOntaCfS 636ttrausfer' ihepositionls owniand Qondenser 357a 'fl t Q vSaid 'PQ iQd 31 5 6?? $955055 The action just described occurs simultaneously in each column wherein a key is depressed. Any column not Contacts $3256 remain closed when no selection is made respective junction 694 is connectedlthrough a resistor .d n a QtedPQ i O QS d pe s i i 7 7 1 0 (via wu're 6 2:. through r 163 the Positive 12; :Apparatus' for 'm ak in"g""magnetic recgrdin s 'repr e -line: 7 4, ljhus, during the i relay R2 is picked up v senting "diflerent valuescomprising rintthe 'rec ording cycle and the grido'f tube 698 is biased ,a; m ag netizable rnediumif r q id n he'. i. highly negative; the junction 6% is preventedifromdropcent the path of moyement "of said ,ntiedr r-r y R2 i ken by switch :62 an iQP o :Ih .p q rs ir lv i iqr stil the, Whi

tacts'546 through relay coil R6 t5line'76f 'Re'lay" R6 Q magnet coil 34 from line 74; via wire 618, throughcpn vent ion as embodied in an apparatus-formakingrnag ing the rate of voltage increase in accordance with the value to be recorded.

3. An apparatus in accordance with claim 2 wherein said last mentioned means consists of a series of condensers of difierent capacities corresponding to the different values to be recorded and means for selectively connecting said condensers to the circuit of the recording head.

4. In an apparatus for making successive magnetic recordings representing different values on a magnetizable medium, the combination of means for advancing said medium in successive steps of predetermined duration, a recording head positioned adjacent the path of movement of said medium, means for applying high frequency alternating current to said recording head during a portion of said advancing movement, means for increasing the voltage of said current at difierent rates comprising a series of condensers of difierent capacities corresponding with the different values to be recorded, condenser selecting means for connecting a condenser to the circuit of the recording head, and a control circuit having means for successively initiating the operation of said advancing means, closing the circuit of the recording head, opening the circuit of the recording head after a predetermined period of recording, and stopping the advancing means.

5. The apparatus of claim 4 wherein means are provided for limiting the increasing voltage applied to the recording head to a predetermined maximum and maintaining such maximum voltage until the end of the recording period.

6. In an apparatus for making successive rows of magnetic recordings representing different values on a magnetizable medium, the combination of means for advancing said medium in successive steps of predetermined duration, a row of recording heads positioned across the path of movement of said medium, means for applying high frequency alternating currents to said recording heads during a portion of said advancing movement, means for increasing the voltages of said currents at different rates comprising a series of condensers of diiferent capacities corresponding with the different values to be recorded for each recording head, condenser selecting means for connecting condensers to the circuits of the recording heads, and a control circuit having means for successively initiating the operation of said advancing means, closing the circuits of the recording heads, opening the circuits of the recording heads after a predetermined period of recording, and stopping the advancing means.

7. The apparatus of claim 6 wherein means are provided for limiting the increasing voltages applied to the recording heads to a predetermined maximum and maintaining such maximum voltage until the end of the recording period.

8. In an apparatus for making successive rows of magnetic recordings representing different values on cards of magnetizable material, a row of recording heads, a card magazine, card feeding means for advancing a card from said magazine to said recording heads, then advancing said card in successive periods of predetermined duration across said recording heads in a direction transverse to said row and thereafter discharging said cards, means for applying alternating current of predetermined and uniform high frequency to said recording heads progressively increasing the voltage of said current, during a portion of said successive periods, and means for selectively varying the rates of voltage increase in accordance with the values to be recorded.

9. The apparatus of claim 8 wherein said last named means comprises a keyboard having keys representing the different values to be recorded, a series of condensers of diiferent capacities corresponding to the diflerent values to 'be recorded and means controlled by said keys for connecting the corresponding condensers to the circuits of said recording heads and discharging said condensers during the recording period.

10. Apparatus for making magnetic recordings comprising means for advancing a magnetizable medium, a recording head positioned adjacent the path of movement of said medium, means for applying an alternating current of predetermined and uniform high frequency to said recording head during such movement for a period of predetermined duration, and means for increasing the voltage of said current at a predetermined rate during a portion of said period and maintaining said voltage for the remainder of said period, at the value to which it is increased during the first portion thereof.

11. The apparatus of claim 10 wherein said last named means includes a condenser of predetermined capacity and means for connecting said condenser during its discharge to the circuit of said recording head.

12. Apparatus for generating and recording wave forms of predetermined shape and dimensions comprising a high frequency oscillator, a triode having a resistor, means for feeding the output of the oscillator to the grid of said triode, a second triode connected in parallel with the first triode to said cathode resistor, means for applying a potential to the grid of said second triode and decreasing such potential at a predetermined rate, and means for recording the wave forms produced during the period of application of said potential.

13. The apparatus of claim 12 wherein the potential applied to the grid of the second triode is derived from a charged condenser and is lowered by discharging the condenser at a predetermined rate.

14. The apparatus of claim 12 wherein a rate of discharge proportional to the capacity of the condenser is obtained by maintaining the current of the discharging condenser at a constant value.

References Cited in the file of this patent UNITED STATES PATENTS 1,452,032 Fan-ington Apr. 17, 1923 1,452,339 Heising Apr. 17, 1923 2,080,273 Holmes May 11, 1937 2,168,402 fFitzgerald Aug. 8, 1939 2,247,905 Bryce July 1, 1941 2,560,474 Potts July 10, 1951 2,596,621 Van Loon et al May 13, 1952 2,624,850 Vaughan Ian. 6, 1953 2,699,498 Guenther Jan. 11, 1955 2,784,392 Chaimowicz Mar. 5, 1957 FOREIGN PATENTS 986,551 France Mar. 28, 1951 OTHER REFERENCES Waveforms, M.I.T. Radiation Lab., vol. 19, copyright 1949, PP. 377-378. 

